The present invention relates to a throw-away cutting tool such as a tool, a boring bar, or a milling cutter having an indexable cutter insert (hereinafter referred to simply as "bit") mounted to a bit mounting seat formed at the front portion of a tool body, and in particular, relates to a cutting tool having a shank made of cemented carbide and the bit mounting seat made of steel or sintered metal capable of machining.
A cutting tool such as a tool, a boring bar, or a milling cutter having a shank made of cemented carbide in order to increase the damping capacity and to restrain chatter of the tool body is known. However, in a throw-away cutting tool mounted with a bit employed as a cutting edge, a bit mounting seat cannot be easily formed when the tool body is made of cemented carbide. For this reason, in a prior art cutting tool, the tool body is constructed with a front end portion made of steel or sintered metal and a rear portion made of cemented carbide; the front end portion is formed with a bit mounting seat; the front portion is fixed to the rear portion.
FIGS. 1 and 2 illustrate an example of such a cutting tool. In the Figures, a tool body 1 consists of a cylinder-shaped shank 2 made of cemented carbide and a bit mounting component 3 made of steel or sintered metal. The bit mounting component 3 is formed with a bit mounting seat 4 at the front portion thereof. A bit 5 is secured to the bit mounting seat 4 by a clamping mechanism 6. The rear end 3A of the shank 2 is formed into a cylinder shape having the same diameter as the shank 2. The front end 3B of the bit mounting component is formed into a semicircular cross section by removing the upper half portion of the front end 3B from a plane including an axis O of the cylinder. The rear end face of the bit mounting component 3 is soldered to the front end face of the shank 2 so that the bit mounting component 3 is fixed to the shank. The upper plane face 3C of the bit mounting component 3 is provided with a bit mounting seat 4 and a clamping mechanism 6.
The bit is formed as a positive type bit having an upper face 3C used for a cutting face 3C in the shape of an equilateral triangle. A plurality of cutting edges 5C are formed at the intersections between the upper face 3C and three side faces 5B used for flank faces. The bit mounting seat 4 for mounting the bit 5 is defined by a bottom wall 4A recessed from the upper plane face and side walls 4B and 4C rising up from the bottom wall 4A. The angle between the side walls 4B and 4C is set at 60.degree.. The bit mounting seat 4 is arranged such that the cutting edge 5C of the bit 5 is perpendicular to the axis O of the circular cylinder and slightly projects from the bit mounting component 33 in the direction of the axis O.
The clamping mechanism 6 consists of a clamping bolt 6A secured to the bit mounting component 3 and a clamping piece 6B having a clamping claw 6C at the front end thereof, so that the upper face 5A is pressed by the claw 6C, and lower face 5D opposite to the upper face 5A is adhered to the bottom wall 4A so as to secure the bit 5 to the bit mounting seat 4. The position of the bit 5 is fixed by contacting two of three side faces 5B with the side walls 4B and 4C and by securing the bit 5 with the clamping mechanism 6. A relief 4D is formed at the intersection of the side walls 4B and 4C.
In the above constructed throw-away cutting tool, the tool body 1 is constructed by means of soldering the front face of the cylinder shaped shank 2 to the rear end face, which has the same diameter as the shank 2 of the bit mounting component 3. Therefore, the soldered layer between the front end face of the shank 2 and the rear end face of the bit mounting component 3 exists along the direction perpendicular to the axis O of the tool body 1.